Field of the Invention
The invention relates to an apparatus for synchronizing transfers of a sheet material, such as sheets of paper or board to be printed during their transport through sheet-processing machines such as rotary printing machines.
Published, Non-Prosecuted German Patent Application DT 25 01 963 A1 relates to a gripper carriage drive. In a printing machine having a feeder and a deliverer unit, the sheet to be printed is preferably guided on horizontal paths in the grip of a gripper. The gripper carriages in each case carrying the individual sheets function as armatures with the printing-unit and return running rails which are disposed on both sides in the side walls of the printing machine, form an endless belt and function as stators. Together with the printing-unit and return running rail functioning as stators, the gripper carriages each form a linear motor connected to a control device. This solution constitutes the coupling of machine groups to linear drives that are guided on a closed circular path.
During the conveyance of articles, such as sheets to be printed, through the printing units of multicolor rotary printing machines, the articles are transferred from one transport system to the following transport system at the interfaces between the transport systems used there. In the case of rotary printing machines, the sheet material is transferred from one cylinder to the next by the gripper systems of the two cylinders holding the sheet simultaneously for a brief moment. The preceding system is then opened and the sheet material is still held only by the following system. The transfer necessitates mechanical components inter-engaging. The mechanical coupling of the cylinders via the gear train ensures the accurate-register transfer of the sheet material and the collision-free dipping action of gripper bars in one another.
However, if the drives of the cylinders of printing units in rotary printing machines are configured as individual drives, so that there is no longer any mechanical coupling of the cylinders to the gear train, in the event of a failure of a drive, caused by faults in the electronic control and motor, it is no longer ensured that the gripper bars gripping the sheet material will dip into one another without collision. The same problem arises when linear units are used for the sheet transport, and the sheet material is held and conveyed by gripper bars that are driven on one or both sides by linear motors. The sheet material is then transferred by the linearly moved gripper bar to the respective next cylinder. If components of the individual drive fail here, it is also necessary to ensure that gripper bars and cylinders do not collide with one another. Published, Non-Prosecuted German Patent Application DT 25 01 963 A1, mentioned at the beginning, discloses a machine concept in which linearly driven gripper bars transport paper sheets through a rotary printing machine with printing units disposed one behind another. In this solution, machine groupsxe2x80x94gripper carriages herexe2x80x94are coupled by linear drives that are guided on a closed circular path.
The configuration does not have any mechanical collision safeguard to prevent the gripper bars being drawn into the printing units. Transfer units based on linear motors, which implement the transfer of the sheet material or the transfer of sheet material from and to printing-unit cylinders, have hitherto been configured without any collision safeguard. This results in an availability deficit in the event of faults, since the remaining components of the rotary printing machine are in this case not protected against collision of mechanical parts.
One previously known possible solution to the technical problem indicated is to synchronize the gripper bars that are fastened to chains with the cylinders. This is achieved by gripper bars fixed to chains being fixed by prismatic elements between impression cylinder and blanket cylinder.
It is accordingly an object of the invention to provide an apparatus for synchronizing transfers of sheet material which overcomes the above-mentioned disadvantages of the prior art devices of this general type, which ensures the collision-free entry of linearly driven holding devices conveying the sheet material, and also the collision-free passage of the holding devices, along the press nip and to prevent damage to cylinders processing the sheet material.
With the foregoing and other objects in view there is provided, in accordance with the invention, an apparatus for transporting a sheet material in a sheet-processing machine having individual stations with cylinders. The apparatus contains a transport system for the sheet material having drives driven independently of the cylinders of the individual stations processing the sheet material in the sheet-processing machine; and at least one cylinder-coupled collision safeguard functioning as a synchronization mechanization bringing about a synchronization of the transport system conveying the sheet material and the cylinders.
By the solution proposed according to the invention, both the maintenance of the register accuracy and the avoidance of collisions may be implemented by various elements. While the maintenance of register is substantially achieved by the use of mutually synchronized electronically controlled drives, the mechanical elements which are proposed in accordance with the invention and are mechanically coupled to the cylinders accommodated, for example, in the printing unit of a rotary printing machine, ensure protection against collision of moving machine parts. According to the solution proposed in accordance with the invention, the coupler drives monitoring a small movement area with regard to the collision are assisted by mechanical safety elements which can be retracted, so that the collision-free entry of the gripper bars conveying the sheet material into the printing area is ensured in the case of advanced or retarded gripper bars (during disrupted operation).
With the solution proposed in accordance with the invention, it is further possible, in the case of linearly driven gripper bars which are merely used to transfer the sheet between the printing unit and the deliverer, to ensure collision-free operation, in particular prevent damage to the expensive and complicatedly produced cylinders, in the event of failures.
In order to rule out the situation where the complicatedly and expensively produced cylinders in the printing unit of a rotary printing machine are damaged in the event of fault by the asynchronous entry of units conveying the sheet material, it is ensured that the elements preventing the collision in the printing unit of a rotary printing machine are coupled precisely to the cylinders to be protected.
In a development of the idea according to the invention, as a collision safeguard in printing units of rotary printing machines, synchronization mechanisms are used whose output movement is coupled to the position of a transverse cylinder and/or a cylinder carrying the sheet material. The cylinders substantially to be protected against collision with gripper bars in the printing unit are the blanket cylinder that transfers the ink to the surface of the sheet material and also the paper-carrying impression cylinder supporting the sheet material in the printing unit of a rotary printing machine. If, in the event of turner devices being used in rotary printing machines, anti-smear coatings are applied to the impression cylinder, the protection of its surface finished in such a way is all the more important.
According to a further aspect of the solution proposed in accordance with the invention, an output element of the synchronization mechanism functioning as a collision safeguard is driven at a higher speed as compared with the tangential speed of the linear element conveying the sheet material. In this way, before the gripper element gripping the sheet material dips into the press nip with the tangential speed, it is possible to achieve the situation where the output element carries out a catching-up movement, so that it is ensured that linear units, that is to say gripper bars driven by linear units, which arrive xe2x80x9cretardedxe2x80x9d are drawn positively through the channel of the cylinder.
According to the invention, it is further proposed to construct the synchronization mechanism as a flexible drive mechanism, whose circulating flexible drive drives an operating element on the respective cylinder with a speed profile which overtakes or catches up as compared with the rotating cylinder. By the solution, it is possible to ensure that, in the event of a fault, linear units gripping the sheet material and arriving retarded can be set into a collision-preventing position in relation to the rotating cylinders in the printing unit of a rotary printing machine.
The synchronization mechanisms proposed in accordance with the invention contains transmission elements of which one is accommodated on a pivot mounted offset in relation to the axis of rotation of the corresponding cylinder. In order to offset the pivot, it may be expedient, using a centrally mounted crank rocker, to use two inter-meshing gearwheels. Advantageously fixed to the output pinion of the pair of gearwheels is the crank that introduces the rotational movement into a coupler that, in turn, represents the output element. Using this configuration, an output drive movement is obtained which produces a catching-up movement shortly before the critical point occurs for avoiding a collision between the cylinder circumference, that is to say its outer surface, and the gripper bar which fixes the sheet material and is arriving retarded as the result of a fault.
By the coupler mechanisms functioning as the synchronization mechanisms in the printing unit of a rotary printing machine in order to avoid collisions between the cylinders and the linear units conveying the sheet material, it is possible to ensure the freedom from collision only within a small area, as a result of the configuration. Therefore, in a development of the idea on which the invention is based, it is proposed to use flexible drive mechanisms which circulate in a form-fitting manner with the cylinders of a printing unit of a rotary printing machine and are driven synchronously. The flexible drive mechanisms preferably circulate at the tangential speed of the cylinders of the printing unit of a rotary printing machine.
Advantageously introduced into the flexible drive mechanisms are openings prepared as slots which constitute dip-in areas for safety elements which are accommodated on the carriages of the linearly driven gripper bars which, in turn, convey the sheet material through the rotary printing machine. The length of the individual openings configured as slots in the flexible drive mechanism determines the area in which the carriage of the relevant linear unit can be positioned. If a carriage of a linear unit retarded because of a fault misses the opening area of the slot, the spring-loaded bolt functioning as a safety device is not able to engage in the slot and travels with one of its ends against a catching edge provided on the frame. The carriage of the gripper bars driven by linear drives are provided with bolt-like safety elements which, for the purpose of gradual braking, are provided with a stop surface which, when they run onto a brake chamfer or when they enter a continuously tapering gap, can effect gradual braking of the carriages of the linear units, so that no abruptly occurring shocks are introduced into the rotary printing machine.
Instead of safeguarding the cylinders by the position of the carriages of the linear units in relation to the circulating flexible drive mechanisms, the synchronization mechanisms functioning as coupler mechanisms may also be associated with cam-controlled catching devices, which enable or prevent the passage of a carriage of a relevant linear unit having a gripper bar in the linear guides. The catching devices contain a cam disk, which has mutually different radial areas including transition areas, whose setting against the bolt-like catching fingers effects their insertion and retraction movement into the linear guides guiding the carriages of the linear units.
In a development of the idea on which the invention is based, catching disks functioning as stops can be provided at the ends of the cylinders of a printing unit of a rotary printing machine, and are provided on the circumference with recesses, which are aligned with the respective channels in the cylinders of the sheet-processing machine. This prevents gripper bars being drawn into the printing units in the event of a collision, that is to say in the event of the presence of a fault in the linear drive of the gripper bars. By use of the stop surfaces of the catching disks, poorly synchronized or unsynchronized gripper bars may be intercepted. The synchronization grooves of the catching disks are made around the channels of the cylinders of the printing unit and are dimensioned such that the linear drives are able to position the gripper bars fixed to them exactly in the press nip. If the drives miss the groove, they are braked by the catching disks in such a way that destruction of the expensively and complicatedly produced cylinders in the printing unit of a rotary printing machine can definitely be prevented.
In a further variant of the solution proposed in accordance with the invention, a stop finger that can be controlled by a cam disk is disposed on a cylinder, the cam disk being driven directly by the rotation of the cylinder to be protected against damage arising from collisions, and the cam disk connecting on a catching element which can be moved vertically. In addition, it is likewise conceivable to dispose segments on the ends of the cylinder cams to be protected against collision, the segments extending stop fingers directly into the conveying path for the gripper bars conveying the sheet material through the rotating system.
The solution proposed in accordance with the invention may be used both in rotary printing machines with and without a turner device; in addition, in multicolor rotary printing machines, which can both be equipped with and without a turner device turning the sheet material. In addition, possible uses of the apparatus proposed in accordance with the invention are provided in sheet-processing machines that operate in accordance with the digital printing process. Further possible uses for the apparatus proposed in accordance with the invention for preventing collisions between moving machine components are to be seen in further-processing units such as stack-forming binding devices and the like.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an apparatus for synchronizing transfers of sheet material, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.